Exoplanet Has Showers of Pebbles

mmmscience writes "The newly-discovered exoplanet COROT-7b has an unusual form of precipitation: rocks. Because it orbits so close to its sun, the temperature on its sun-facing side is around 4220 degrees Fahrenheit. That's hot enough for rocks to vaporize — not unlike water evaporating on Earth. And, like Earth, when the vapor cools in the upper atmosphere, it forms clouds and begins to rain. But instead of water, COROT-7b gets a shower of pebbles."

Comments

Summary inaccurate

[JoshuaZ]

This is a hypothesized event. The evidence for it is slim based primarily on modeling. While this is really cool if correct, one needs to understand that this isn't by any means a slam dunk.

Re:Summary inaccurate

[Sockatume]

To be fair, the original press release also mangles observed and simulated results like crazy. They've definitely found the exoplanet and determined its orbit and mass. They've either confirmed or hypothesised from simulation that there are no volatile compounds on or around the planet, which they hypothesise is due to bake-out. They've hypothesised based on simulations that it is likely to have a rock-based atmosphere which, depending on composition, could be verified spectroscopically.

Re:Not unusual

[Thelasko]

We get solid precipitation here on earth all the time.

The parent raises a good point. How do we know the rock comes back down to the surface as a solid? Why doesn't it rain lava?

Re:Rock Rainbows?

[Gotung]

Not to rain on your rainbow parade, but any planet that close to its star is likely tidally locked.

So no sunset.

Re:Rock Rainbows?

[Jerf]

I would also observe that "molten rock" is not famous for its transparency, let alone "gaseous rock". It may be an "atmosphere", but there won't be anybody observing any sort of "rainbow". The word "atmosphere" may be deceptive in this context; think less "open sky" and more "sea of blindingly hot lava so hot it's gaseous, not that you have any reason to care about this distinction".

Re:Let's not exaggerate

[Sockatume]

Actually a 75m section of a 2000m cylinder, from pi * r^2 * depth comes out at about 200 MILLION cubic metres. Multiply that by about two metric tonnes per cubic metre (sandstone) and you get four hundred million metric tonnes. I can't be bothered to account for the curvature of the crater, but I doubt it'll bring that down much under a hundred million tonnes. There's still the "vapourisation versus excavation" question, of course, I'm just pointing out that your estimate of mass is off by three orders of magnitude.